Salicylates have been implicated in several toxic reactions in man including hepatic and renal necrosis and analgesic nephropathy. We have undertaken the synthesis of potentially toxic metabolites of salicylic acid in order to help elucidate the mechanism of these toxicities. Radiolabeled C 14-gentisic acid has been prepared and initial studies have shown that it covalently binds to microsomal protein. Additional syntheses and experiments in vivo and in vitro with gentisic acid and other metabolites of salicylic acid are now being carried out.